{"id":29410,"date":"2025-08-13T10:46:47","date_gmt":"2025-08-13T09:46:47","guid":{"rendered":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=29410"},"modified":"2025-08-13T10:48:35","modified_gmt":"2025-08-13T09:48:35","slug":"energy-decomposition-analysis-of-hindered-alkenes-tetra-t-butylethene-and-others","status":"publish","type":"post","link":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=29410","title":{"rendered":"Energy decomposition analysis of hindered alkenes: Tetra t-butylethene and others."},"content":{"rendered":"
\n

In the previous post,[1]<\/a><\/span> I introduced the N=N double bond in nitrosobenzene dimer, arguing that even though it was a formal double bond, its bond dissociation energy made it nonetheless a very weak double bond! This was backed up by a technique known as energy decomposition analysis or EDA. Here I use a variant of this method \u00a0known as \u00a0NEDA to look at some other strained alkenes, including the famously non-existent tetra t-Butyl ethene.<\/p>\n

\"\"<\/a><\/p>\n

The NEDA procedure gives a fragment interaction energy (decomposing it into fundamental quantum mechanically derived energies if required) with respect to a reference state for the fragments. In this case, the fragments are obtained by cutting the double bond, resulting in triplet state carbenes as the reference state. The calculations (B3LYP+GD3+BJ\/Def2-TZVPP) are available here.[2]<\/a><\/span><\/p>\n

    \n
  1. Compound 1<\/strong>, a relatively unstrained alkene, \u0394E = -177.0 kcal\/mol<\/strong>, RCC<\/sub> 1.341\u00c5<\/li>\n
  2. Compound 2<\/strong> (PUVQUE, [3]<\/a><\/span>, [4]<\/a><\/span>), \u0394E = -164.3 kcal\/mol,<\/strong> RCC<\/sub> 1.362\u00c5, CC torsion 16.5\u00b0<\/li>\n
  3. Compound 3<\/strong> (CUBVOK, [5]<\/a><\/span>) \u0394E = -167.9 kcal\/mol,<\/strong> RCC<\/sub> 1.351\u00c5, CC torsion 9.2\u00b0<\/li>\n
  4. Compound 4<\/strong> (currently unknown) \u0394E = -135.8 kcal\/mol<\/strong>, RCC<\/sub> 1.380\u00c5, CC torsion 54.5\u00b0<\/li>\n<\/ol>\n

    The NEDA interaction energy is directly proportional to both the CC bond length and the C-C=C-C torsion angle. What is interesting however is the large interaction energy gap in \u0394E between the two known hindered alkenes (2<\/strong> and 3<\/strong>)\u00a0and the unknown tetra-t-butyl ethene 4<\/strong>. It seems moving from say compound 2<\/strong> by converting the two iso-propyl substituents to full t-butyl ones is just too large a change to bridge. Unless one day isolated as a very very unstable species, compound 4<\/strong> seems destined not to exist!<\/p>\n

    \n

    This post has DOI: 10.59350\/rzepa.29410<\/a><\/p>\n

    References<\/h2>\n
    1. H. Rzepa, \"The mysterious N=N double bond in nitrosobenzene dimer.\", 2025. https:\/\/doi.org\/10.59350\/rzepa.29383<\/a>\n\n<\/li>\n
    2. H. Rzepa, \"Energy decomposition analysis of hindered alkenes: Tetra-tert-butyl ethene and others.\", 2025. https:\/\/doi.org\/10.14469\/hpc\/15463<\/a>\n\n<\/li>\n
    3. R. Boese, W.R. Roth, D. Bl\u00e4ser, R. Latz, and A. B\u00e4umen, \"(<i>E<\/i>)-3,4-Diisopropyl-2,5-dimethylhex-3-ene at 125K\", Acta Crystallographica Section C Crystal Structure Communications<\/i>, vol. 54, pp. IUC9800055, 1998. https:\/\/doi.org\/10.1107\/s0108270198099247<\/a>\n\n<\/li>\n
    4. Boese, R.., Roth, W.R.., Blaser, D.., Latz, R.., and Baumen, A.., \"CCDC 130610: Experimental Crystal Structure Determination\", 1999. https:\/\/doi.org\/10.5517\/cc4cx7m<\/a>\n\n<\/li>\n
    5. J. Deuter, H. Rodewald, H. Irngartinger, T. Loerzer, and W. L\u00fcttke, \"Kristall- und molekularstruktur von tetrakis(1-methylcyclopropyl)ethylen\", Tetrahedron Letters<\/i>, vol. 26, pp. 1031-1034, 1985. https:\/\/doi.org\/10.1016\/s0040-4039(00)98504-6<\/a>\n\n<\/li>\n<\/ol>\n\n<\/div> ","protected":false},"excerpt":{"rendered":"

      In the previous post, I introduced the N=N double bond in nitrosobenzene dimer, arguing that even though it was a formal double bond, its bond dissociation energy made it nonetheless a very weak double bond! This was backed up by a technique known as energy decomposition analysis or EDA. Here I use a variant of […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"jetpack_post_was_ever_published":false,"_jetpack_newsletter_access":"","_jetpack_dont_email_post_to_subs":false,"_jetpack_newsletter_tier_id":0,"_jetpack_memberships_contains_paywalled_content":false,"_jetpack_memberships_contains_paid_content":false,"activitypub_content_warning":"","activitypub_content_visibility":"","activitypub_max_image_attachments":5,"activitypub_interaction_policy_quote":"anyone","activitypub_status":"","footnotes":"","jetpack_publicize_message":"","jetpack_publicize_feature_enabled":true,"jetpack_social_post_already_shared":true,"jetpack_social_options":{"image_generator_settings":{"template":"highway","default_image_id":0,"font":"","enabled":false},"version":2}},"categories":[4],"tags":[],"ppma_author":[2661],"class_list":["post-29410","post","type-post","status-publish","format-standard","hentry","category-interesting-chemistry"],"yoast_head":"\nEnergy decomposition analysis of hindered alkenes: Tetra t-butylethene and others. - Henry Rzepa's Blog<\/title>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=29410\" \/>\n<meta property=\"og:locale\" content=\"en_GB\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"Energy decomposition analysis of hindered alkenes: Tetra t-butylethene and others. - Henry Rzepa's Blog\" \/>\n<meta property=\"og:description\" content=\"In the previous post, I introduced the N=N double bond in nitrosobenzene dimer, arguing that even though it was a formal double bond, its bond dissociation energy made it nonetheless a very weak double bond! This was backed up by a technique known as energy decomposition analysis or EDA. 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One of the properties of this molecule is that the equilibrium between the monomer and dimer can be detected,\u2026","rel":"","context":"In "Interesting chemistry"","block_context":{"text":"Interesting chemistry","link":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?cat=4"},"img":{"alt_text":"","src":"","width":0,"height":0},"classes":[]},{"id":30890,"url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=30890","url_meta":{"origin":29410,"position":1},"title":"Valence bond representations with +ve charges on adjacent atoms? An odd titanium complex analysed.","author":"Henry Rzepa","date":"March 8, 2026","format":false,"excerpt":"A few posts back, I contemplated the curly arrows appropriate for the formation of nitrosobenzene dimer from nitrosobenzene, and commented on the odd nature of the N=N double bond formed in this process.. Odd, because the valence bond representation of this dimer (1 below) has two formally positive adjacent nitrogen\u2026","rel":"","context":"In "Interesting chemistry"","block_context":{"text":"Interesting chemistry","link":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?cat=4"},"img":{"alt_text":"","src":"","width":0,"height":0},"classes":[]},{"id":29626,"url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=29626","url_meta":{"origin":29410,"position":2},"title":"Hydrogenating the even more mysterious N\u2261N triple bond in a nitric oxide dimer.","author":"Henry Rzepa","date":"August 25, 2025","format":false,"excerpt":"Previously I looked at some of the properties of the mysterious dimer of nitric oxide \u00a01 - not the known weak dimer but a higher energy form with a \"triple\" N\u2261N bond. This valence bond isomer of the weak dimer was some 24 kcal\/mol higher in free energy than the\u2026","rel":"","context":"In "Interesting chemistry"","block_context":{"text":"Interesting chemistry","link":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?cat=4"},"img":{"alt_text":"","src":"","width":0,"height":0},"classes":[]},{"id":29429,"url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=29429","url_meta":{"origin":29410,"position":3},"title":"The even more mysterious N\u2261N triple bond in a nitric oxide dimer.","author":"Henry Rzepa","date":"August 18, 2025","format":false,"excerpt":"Previously, I pondered about the strange N=N double bond in nitrosobenzene dimer as a follow up to commenting on the curly arrow mechanism of the dimerisation. By the same curly arrow method, one can produce the below, showing how the simpler nitric oxide radical could potentially dimerise to a species\u2026","rel":"","context":"In "Interesting chemistry"","block_context":{"text":"Interesting chemistry","link":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?cat=4"},"img":{"alt_text":"","src":"","width":0,"height":0},"classes":[]},{"id":18165,"url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=18165","url_meta":{"origin":29410,"position":4},"title":"\u03c0-Facial hydrogen bonds to alkenes (revisited): how close can an acidic hydrogen approach?","author":"Henry Rzepa","date":"April 15, 2017","format":false,"excerpt":"Back in the early 1990s, we first discovered the delights of searching crystal structures\u00a0for unusual\u00a0bonding features. One of the first cases was a search for hydrogen bonds formed to the\u00a0\u03c0-faces of alkenes and alkynes. 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